The immunochemical fecal occult blood test is a useful noninvasive tool to screen for bleeding without symptoms in the lower GI tract. If bleeding is discovered, a colonoscopy is then used to investigate the source of bleeding.

Researchers from Taiwan sought to assess the specificity of iFOBT, looking at a group of 2796 people (1654 men and 1142 women) who underwent voluntary bi-directional endoscopies and an iFOBT. The mean age was 49 years. Participants underwent an iFOBT, blood tests, colonoscopy and an upper GI tract endoscopy as well as interviews. All were asymptomatic of bleeding and of major GI disorders.

In Taiwan, colorectal cancer is increasing, and ulcers and other upper GI tract issues are common. Same-day upper GI tract endoscopies and colonoscopies are commonly used to screen for cancer.

Of the total participants in the study, 397 people (14.2%) had a positive iFOBT result, indicating bleeding. The iFOBT was specific for almost 90% of colorectal cancers, adenomas and important lower GI lesions. Lower GI lesions were more common (24.1%) compared with those in the upper GI tract (17.9%). Lesions in the lower GI tract were more frequent in iFOBT-positive screens than in negative screens (41.3% versus 21.3%), whereas the frequency of lesions in the upper GI tract was similar in both positive and negative screens.

"Among participants found to have a malignant lesion, almost all who had colon cancer had a positive fecal test result (27/28, 96.4%). In contrast, none of the three participants found to have esophageal or gastric cancer had a positive fecal test result," writes Ming-Shiang Wu, Department of Internal Medicine, National Taiwan University, Taiwan, with coauthors.

"We found that the specificity of the immunochemical fecal occult blood test was almost 90% for predicting colorectal cancer, adenoma or any important lesion in the lower gastrointestinal tract. These findings support those of previous studies showing that the immunochemical fecal test is a specific diagnostic tool,"" write the authors.